How does a 3-D printer work?

Printing a 3-D object is 'like baking a sliced loaf of bread in reverse.'

A collage of MakerBot users. MakerBot is just one of the 3-D printer options out there for consumers. (Photo: MakerBot)

From working guns to a dead king’s face, we’ve seen some pretty weird things created with a 3-D printer. It may seem like science-fiction, but it seems almost certain that 3-D printing will play a significant role in many industries of the future.

As environmentalists, there’s good reason to be optimistic.

3-D printing could greatly reduce the amount of materials needed in manufacturing everyday items, and it would eliminate the need for a complicated, resource-intensive supply chain. (Why ship parts across the world when you can print them at your desk or local shop?)

As someone who has always struggled with the intricacies of science and engineering, I thought it was about time I found out.

A 3-D printer colors some materials for a coiled sculpture. (Photo: oskay/Flickr)

Printing in layers

When the U.K.’s Independent newspaper tackled this same question in its feature on 3-D printing for dummies (sounds like me!), they described the process as “like baking a sliced loaf of bread in reverse.”

This analogy is actually pretty useful. The printer prints an object in extremely thin slices, and then layers them up, melding them together as it goes.

And the answer to that is in Computer Aided Design (CAD). Using one of the many CAD software products available, a designer can create a 3-D representation of an object (or objects, if what you are printing requires several component parts), which is then divided into layers within the software, creating the “slices” that the printer uses to construct the object.

Printer owners can also download ready-made designs from the Internet – some of which are free and others that are available for purchase.

A physical representation of the above Voronoi structure of Yoda. (Photo: CreativeTools/Flickr)

Additive manufacturing

Any explanation of the 3-D printing process talks about the difference between additive and subtractive manufacturing. This wording gets dangerously close to technical jargon for my liking. But here’s what it means.

For most of human history, we’ve made things by taking a larger object (a block of wood or granite, for example) and then whittled, ground or filed it down to the size and shape we want. (A spoon, a statue, etc.) This has lately become known as “subtractive manufacture.” Alternatively, we’ve created a mold and then poured a particular material (molten steel, for example) into it – shaping it into an arrow head, or a cog, or whatever it is we need to make. But this process was somewhat time-consuming as it first required the construction of the mold, then the process of using that mold.

Additive manufacturing offers a different vision – allowing for rapid, one-off and extremely precise construction of components and models using readily available raw materials like PET plastics, paper or even chocolate or synthetic meat (more on that later). The manufacturing process uses only the materials needed, greatly reducing or eliminating the problem of waste. And because it encourages the standardization of materials, it should also facilitate the recycling of the raw materials if an object becomes broken or obsolete.

Once a printer receives its instructions in the form of an .STL file (this stands for "Standard Tessellation Language"), it begins printing in minute layers that are a tiny fraction of a millimeter thick. (The thickness varies on the precision-level of the printer, with more expensive models printing thinner, more precise layers.) Those layers are automatically bound together as the printing continues, creating a continuous, 3-D object as a result.

The exact method of printing varies from printer to printer with some, like the MakerBot 2 feeding a spool of bioplastic through the printer head in much the same way as a regular printer would deposit ink on a page. Others distribute powdered material like granular metals or plastics onto a build platform, and then use a laser or binder to fuse layers of the desired object together. Yet others, like the FORM 1, use a tray of liquid resin, which hardens on exposure to a laser.

Right now, it seems 3-D printing is used for items that are one-offs and or need to be highly customized. This includes, for example, architects and engineers creating prototypes, allowing for rapid and cost-effective construction of detailed models. There is also a lively culture of hobbyists, crafts people and inventors using 3-D printers, making everything from jewelry to models to wild ideas they want to explore. Folks are experimenting all the time, and there are plenty of videos on the Internet featuring 3-D printed chocolates, bicycles, guns, cars, houses and even a bikini.

For many objects for which there’s a wider market, mass manufacturing techniques like injection molding are still likely to be significantly cheaper for a long time to come.

But as with the cellphone, or the car, or the Internet — or any new technology for that matter — we should be careful about making too many judgments or predictions about the utility or potential for large-scale adoption. We know the future will look decidedly different from the present, and there’s a high likelihood that distributed 3-D printing will help shape it in ways we can only begin to imagine.

Of course along with all the techno-optimist hype about eliminating shipping and waste, we should note that there are potential downsides too. In a world where everyone can print their own furniture, car or gun at the touch of a button, who’s to say 3-D printing won’t unleash a whole new wave of materialistic consumerism?

Like almost any technology, 3-D printing is neither silver bullet nor potential disaster.

It’s simply a technology. And it’s up to us, as individuals, as a culture, and as a society, to shape how we use it for the benefit of all.